Fuel map dynamic range

[s1k]

Hi

Does anyone else have a problem with dynamic range limitation? See attached fuel map.

My car is running very rich on idle put perfect on high load and full boost. This is not really a problem for everyday or track driving but might hurt the catalyctic converter and makes it impossible to pass inspection here in Sweden. Car is tuned to about 420hp on a dyno by a shop.

My solution so far has been to before inspection set the rev limit to 3000 and adjust K-value until AFR is 14,7:1, then reflash original tune after inspection.

Maybe there is a nicer solution to this issue?

[Matt]

Why is the tune like that? The idle normally starts at +192 (0 filtered) but this is incredibly high at the lower end of the map (around 255)

So it is no wonder it is excessively rich at the bottom end of the map

Which vehicle is this?

[bachig24u]

Due to the obvious 255's (max bin number) everywhere it would indicated to me that a bad read or bad write occurred.
That looks more like an attempt to Track tune a car with auto corrections on high correction limits, maybe a massive exhaust airleak, a very short exhaust that backfires a lot on decel and the use of a highly oxygenated race fuel being used.

it looks like auto tune and closed loop. Hard to imagine it being possible but over hours and hours of driving it has the potential.

[s1k]

Hi and thanks for the replys. The car is a 200sx S14 with SR20DET. Stock top end but pretty high boost (1,5-2,0 bar). Would full spec help to explain the tune?

As far as I know there are no air leaks or anything special with the exhaust (3" with cat).

Sorry but I am no tuning specialist, as I stated it was tuned by a shop on a dyno here in Sweden.

I assume that the bin number 255 is the minimum amount of fuel to the injectors and 0 is the maximum amount of fuel - is this not correct? To me it looks like when K value is set to give all fuel necessary at injector bin number 0 (full boost) the minimum amount on idle is still too much, causing the engine to run rich on idle.

Would not adjusting the low range injector numbers to 192 cause it to run even more rich on idle?

[Matt]

RAW VALUES
0-191 is the range (open loop)
192-255 is the range (closed loop - aqua area)

Change from RAW VALUES to FILTERED VALUES to have it display in a more readable format

Lower values = less fuel => higher values = more fuel

[s1k]

Well that sure might explain some things...

Just to be clear (and make sure I dont misunderstand anything).

RAW value 255 is the maximum amount of fuel with O2 sensor ON
RAW value 192 is the minimum amount of fuel with O2 sensor ON
RAW value 191 is the maximum amount of fuel with O2 sensor OFF
RAW value 0 is the minimum amount of fuel with O2 sensor OFF

Correct? Is there anything else that changes when moving between the closed/open loop areas besides O2 auto adjustment?

I am going to try moving the low load/rpm areas closer to 192 raw and see if idle mixture becomes better.

[bachig24u]

Sorry, I can no longer help at this point.

There is some really good information in the available Nistune manuals and guides. the issues in just the fuel map are huge.

I still can't believe your dyno tuned 420HP 1.5-2Bar boosted engine hasn't dumped its bottom end in the sump.

[s1k]

Sorry, I can no longer help at this point.

There is some really good information in the available Nistune manuals and guides. the issues in just the fuel map are huge.

I still can't believe your dyno tuned 420HP 1.5-2Bar boosted engine hasn't dumped its bottom end in the sump.

Surely its not that bad? The car is running very nicely in the high boost areas with proper AFR values, good exhaust temp and no knocking. Do you see any other obvious problems besides the low load/idle area?

Anyway I think the first question in the thread has been answered. This is NOT a dynamic range problem in the ECU but a tuning error in the low load area. I have no idea why it would be set up like this though... The shop did say that they where new to Nistune so perhaps this is just a misunderstanding from their side.

I also found the reference to the RAW values and O2-sensors flags on page 28 in the Nistune Mapping Guide:
http://nistune.com/docs/Nistune_Mapping_Guide.pdf

0-127 is the range with O2 sensor off (filtered as 0-127) and 128-255 is the range with O2 sensor on (filtered as -64 to 63 with blue color).

I'm gonna try remapping the low load areas on the street myself once it's a bit warmer outside, a completely new tune on a dyno might be in order though.

Thanks for all your help!

[Matt]

Surely its not that bad? The car is running very nicely in the high boost areas with proper AFR values, good exhaust temp and no knocking. Do you see any other obvious problems besides the low load/idle area?

The second (load) half of the map is probably okay, but the first half need to be rectified

Anyway I think the first question in the thread has been answered. This is NOT a dynamic range problem in the ECU but a tuning error in the low load area.

correct

I have no idea why it would be set up like this though... The shop did say that they where new to Nistune so perhaps this is just a misunderstanding from their side.

I think it is

Change the view from 'raw view' to 'filtered view' to get an accurate repesentation of the numbers (they should be going from low > high)

0-127 is the range with O2 sensor off (filtered as 0-127) and 128-255 is the range with O2 sensor on (filtered as -64 to 63 with blue color).

Yes that would be the correct info. But use filtered mode to view it -64 to 63

I'm gonna try remapping the low load areas on the street myself once it's a bit warmer outside, a completely new tune on a dyno might be in order though.

Sounds like a good plan